The present invention relates to a molded and crosslinked rubber material suitable for use as a one-piece golf ball material and as the core material in solid golf balls such as two-piece golf balls and three-piece golf balls. The invention relates also to a method of manufacturing such a molded and crosslinked rubber material.
Golf balls known to the art include solid golf balls composed of a solid core obtained by molding and crosslinking a rubber composition containing various rubber compounding ingredients and a one-layer or multilayer cover which encloses the solid core, and one-piece golf balls obtained by molding and crosslinking a rubber composition and using the resulting spherical object in its entirety as the ball. In these golf balls, a rubber composition composed chiefly of a base rubber is molded and vulcanized to produce a spherical crosslinked molding as the core. By adjusting the hardness difference between the center portion and surface portion thereof, it is possible to increase the degree of freedom in the ball hardness profile. To this end, JP-A 10-43330 discloses a golf ball having a core in which silica particles are included at the core surface as a means for increasing the surface hardness of the ball.
However, in such golf balls, because the silica particles are merely an inorganic filler, the interfacial loss of material arises, worsening the rebound.